1. Field of the Invention
The invention relates to a method for vacuum deposition of circuitry onto a thermoplastic material. In one of its aspects, the invention relates to vacuum deposition of circuitry for automotive applications. In another of its aspects, the invention relates to a vehicular lamp housing incorporating a circuit placed thereon by vacuum deposition. In another of its aspects, the invention relates to a vehicular lamp housing with vacuum deposition of circuitry powering light-emitting diodes. In another of its aspects, the invention relates to a vehicular lamp housing with a vacuum deposition of circuitry powering removable incandescent lamps.
2. Description of the Related Art
It is known to create circuit boards using vacuum deposition on a microscopic scale. In this method, microscopic vacuum deposition is accomplished by use of a focused electron beam to create circuitry tracks on the circuit board. Each track is developed on the circuit board to a thickness of only a few angstroms to provide a circuit capable of carrying the very small currents required by the circuit board.
A larger-scale vacuum deposition process is known in creating reflectorized surfaces such as for the interior of a lamp housing to provide a reflective backdrop for an incandescent lamp for projecting light through a lens covering the lamp housing for observation by other motorists. Such large-scale vacuum deposition is accomplished in a vacuum deposition chamber. Lamp housings to be deposited with the reflective coating are physically masked and passed in front of a chromium target subjected to a high voltage, which causes chromium particles to leave the target and embed in the plastic material of the lamp housing. This process creates a coating of chromium on the plastic housing 200 to 400 angstroms thick on unmasked portions of the lamp housing. The reflectorized lamp housing is then provided with a covering translucent lens and electrical circuits and bulbs as is known in the prior art. Such prior art lamp housings come in many forms.
Referring to one example of a prior art lamp housing assembly shown in FIG. 1, a housing 10 has an inner surface 12, usually coated with a reflective material, and a number of apertures 14 for insertion of lamps 16 from a rear portion of housing 10. The front portion of housing 10 is covered by a translucent lens 18, lens 18 commonly having regions of different colors based on the function of the lamp 16 projecting light through that portion of the lens 18. The individual lamps 16 are provided power through a wire harness 17 connected to each of the lamps 16.
FIGS. 2 and 3 show further prior art embodiments wherein bulbs 16 are each carried by a removable socket 22, and insertion of the socket 22 into the apertures of the housing electrically connects the bulbs 16, in the case of FIG. 2, to a flexible printed circuit 24, or in the case of FIG. 3, to a stamped metal harness 26, the printed circuit 24 or stamped metal harness 26 themselves being electrically connected to the automobile's electrical system to complete a current-carrying circuit. Each of the prior art embodiments of FIGS. 2 and 3 further requires additional interface pieces 28, 30, 32 for attaching and mating the bulbs to the housing 10.
Referring now to FIG. 4, a further embodiment of a prior art lamp housing 40 is adapted to receive a number of light-emitting diodes (LED) 42 held in a snap LED holder 44 constructed with offsets 46 for matching the contour of the housing 40. The front of the housing 40 is covered by a lens 48.
Yet another prior art embodiment is shown in FIG. 5 wherein a housing 50 carries a printed circuit board 52 with a number of LEDs 54 mounted thereon, a reflector 56 covering the printed circuit board 52 with LEDs 54 projecting therethrough, and a lens 58 mounted to the front of the housing 50 to seal the housing 50, holding the printed circuit board 52 and reflector 56 therein.
Each of these prior art lamp housings has inherent disadvantages. The wire harness type lamp housing (FIG. 1) has a high piece price, mechanical size constraints, and is labor intensive to build and install. The flex circuit (FIG. 2) can be costly, and sealing the flex circuit to the housing, as well as the mechanical integrity of the electrical connector to the housing are limiting factors. Servicing, capital equipment costs and installation costs of the assembly are further disadvantages. The metal circuit stamping housing (FIG. 3) has the disadvantages of high tooling costs, handling costs, sealing and installation costs. The flat LED metal frame (FIG. 4) has a high piece price, planar design limitations, limited suppliers, and is limited to LED designs. The LED printed circuit board assembly (FIG. 5) has a high piece price, is limited to a planar design, has high installation costs, and, again, is only for use with LEDs.
It would be advantageous to provide a lamp housing to overcome the disadvantages of the prior art, in that it would be adaptable to use with LEDs as well as conventional incandescent or other available lamp technologies, is adapted for providing different colors of light, specifically white light, and is efficient in both space requirements and installation costs.